JP3203097B2 - Transceiver system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transceiver for communicating with a phase-modulated carrier, for example, a digital cellular telephone,
About the system.

[0002]

2. Description of the Related Art Conventionally, this type of transceiver system includes a transmitter 10 and an receiver 20, which are selectively connected to an antenna 31 via an antenna switch 36 as shown in FIG. I was The transmitter 10 includes a high-frequency amplifier 11, a loosely coupled circuit 12, an envelope detection circuit 13, and a level comparison circuit 14.

The receiver 20 includes a high-frequency amplifier 21 and a mixing circuit 22 in a so-called super heterodyne system. At the time of transmission (the antenna switch 36 is
In this state, the loose coupling circuit 12 extracts a part of the high-frequency signal output from the high-frequency amplifier 11 so as not to affect the output of the antenna 31, and performs envelope detection. The signal is sent to a circuit 13 and subjected to envelope detection. The detection output level is compared with a fixed voltage having a predetermined level provided in the level comparison circuit 14.
The difference is input to the high frequency amplifier 11.

Here, the high-frequency amplifier 11 employs a bias system in which the amplification factor is changed according to the output level sent from the level comparison circuit 14. The amplification factor is controlled by the change in the difference, and the high-frequency signal output is controlled. Is adjusted to a predetermined size. On the other hand, during reception (the state in which the antenna switch 36 connects the receiver 20 and the antenna 31), after the reception signal from the antenna 31 is amplified by the high-frequency amplifier 21, the mixing circuit 22 Output (not shown)
To extract a signal having a frequency that is the difference between the two.

Here, the level of the received signal received from the antenna 31 of the transceiver is not constant. For example, the closer the receiving position is to the base station that oscillates the signal, the higher the level of the received signal is. It will be. Therefore, in the above-described conventional device, when a large-level received signal enters the antenna 31, the received signal from the antenna 31 is amplified by the high-frequency amplifier 21 at a uniform amplification rate regardless of the magnitude of the signal level. Therefore, a large-level signal is sent to the mixing circuit 22 at the subsequent stage.

However, in the phase modulation system, the information changes when the received signal is distorted. To prevent this, the mixing circuit 22 outputs the large-level signal with a magnitude proportional to the level. Must.
Therefore, in the mixing circuit 22 in the above-described conventional system, an element having a wide linearity region (a region where the input level and the output level are linear) must be used.

[0007]

However, an element having a wide linearity region is expensive, and a system using this element has a disadvantage of being expensive. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a transceiver system capable of processing a received signal without distortion without using an element having a wide linearity region in a mixing circuit even when the received signal level is large. The purpose is to provide.

[0008]

According to the present invention to achieve the above object, a transmitter and a receiver are selectively connected to an antenna via an antenna switch, and the transmitter includes a phase-modulated high-frequency output. later was detected by envelope detection circuit is compared with a reference level at the level comparing circuit, and configured to control the transmission output level in comparison of that, the receiver is pre
A high-frequency amplifier is installed to amplify the signal received from the antenna.
In vignetting the transceiver system, the input side of the envelope detection circuit, the antenna switch, when said transmitter and said antenna <br/> Na is connected, a high-frequency output signal of the transmitter the input to envelope detector circuit, when said a <br/> antenna and the receiver is connected, the switch to enter the received signal from the en <br/> antenna to the envelope detection circuit one switch is provided, whereas, on the output side of the record <br/> level comparator circuit, by the first switch, when the high frequency output signal of the transmitter is input to the envelope detection circuit, It switched to control the transmission output level by the output of said level comparator circuit, before
When the received signal by the serial first switch is input to the envelope detection circuit, the second switch switched to control the amplification factor of the high frequency amplifier at the receiver side by the output of said level comparator circuit It is characterized by being provided.

[0009]

When the antenna is connected to the receiver, the signal received from the antenna enters the envelope detection circuit via the first switch, is envelope-detected, and is detected by the level comparison circuit.
The result is compared with the reference level, and the result of the comparison is output to the high-frequency amplifier via the second switch to control the amplification factor.

Here, if the gain is controlled to be small if the difference between the received signal level and the reference level is large, if a large level signal enters the antenna, the high-frequency amplifier will have a small gain. Amplifies the received signal and prevents sending a high-level signal to the mixing circuit. Therefore, an element having a small linear region can be used as the mixing circuit.

When the antenna and the transmitter are connected, the high-frequency signal of the transmitter enters the envelope detection circuit via the first switch, is envelope-detected, and is detected by the level comparison circuit. The signal is compared with the reference level, and the comparison result is sent to the transmitter via the second switch, and the transmission output level is controlled.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a transceiver system according to the present invention will be described with reference to the drawings. The transceiver system is roughly divided into a transmitter 10, a receiver 20, a first switch 32 for switching a path between the transmitter 10 and the receiver 20,
It comprises a second switch 33 and a bias switching circuit 34 for controlling the amplification of the received signal.

Although not particularly described, it is assumed that the transmission / reception signal is modulated by (π / 4) QPSK as an example of the phase modulation method. First, the configurations of the transmitter 10 and the receiver 20 will be described. As shown in FIG. 1, the transmitter 10 includes a high-frequency amplifier 11, a loose coupling circuit 12, an envelope detection circuit 13 which is one of detection circuits, and a level comparison circuit 14, and the receiver 20 includes a high-frequency amplifier 21 , A mixing circuit 22, and alternatively connected to the antenna 31 via an antenna switch 36.

The high-frequency amplifiers 11 and 21 amplify the level of an input signal with a predetermined amplification factor.
An element is used. Among these, the amplification factor of the high-frequency amplifier 11 on the receiver 20 side is controlled by the output of the bias switching circuit 34 described in detail later. The loosely coupled circuit 12
A signal is taken out by loose coupling that does not affect the level of the high-frequency signal amplified by the high-frequency amplifier 11, for example, a low-capacity capacitor.

The envelope detection circuit 13 is a known circuit that detects and outputs a waveform corresponding to an envelope of a high-frequency signal. The level comparison circuit 14 uses a comparator that compares the level of the transmitted signal with a fixed voltage provided in advance. The mixing circuit 22 is a known circuit that mixes a received signal with a local oscillation output (not shown) and extracts a signal having a frequency difference between the two.

As shown in FIG. 1, the first switch 32 is a switch for selectively switching between two contacts, a common contact is connected to the input side of the envelope detection circuit 13, and one of the two contacts is connected. Is connected to the loosely coupled circuit 12 of the high frequency amplifier 11 and the other is connected to the antenna 31 side. Second switch 3
Reference numeral 3 denotes a configuration similar to that of the first switch 32. The common contact is connected to the output side of the level comparison circuit 14, and the two contacts are connected to the high-frequency amplifier 11 side and the bias switching circuit 34 side.

As shown in FIG. 2, the bias switching circuit 34 includes two transistors Q22 and Q23 and two resistors R1 and R2 forming an output circuit. When the level comparison circuit 14 determines that the difference between the received signal and the reference voltage is within the set range, the signal is transmitted to the transistor Q22.
Is added to the base circuit. When the difference between the received signal and the reference voltage is within the set range, the base circuit hardly flows the base current and keeps transistor Q22 non-conductive.

When transistor Q22 is turned off, transistor Q23 is also turned off, and no current flows through its collector circuit. Therefore, the high voltage Ve is directly applied to the gate circuit of the high frequency amplifier circuit 21. For this reason, the amplification factor is maintained at a normal high state. on the other hand,
When the level comparison circuit 14 determines that the difference between the received signal and the reference voltage is out of the set range, the signal is applied to the base circuit of the transistor Q22 and the transistor Q22
22 is made conductive.

When the transistor Q23 is turned on, the transistor Q23 is also turned on and a collector current flows through the two resistors R1 and R2. As a result, the voltage of the gate circuit of the high-frequency amplifier 21 is reduced to (R2 / (R1 + R2)) Ve. Therefore, the amplification factor of the high-frequency amplifier 21 decreases. Hereinafter, the operations at the time of transmission and at the time of reception will be described. ,
At the time of transmission, the antenna switch 36, the first switch 32, and the second switch 33 have been switched to the states shown in FIG.

Therefore, the high-frequency signal input to the high-frequency amplifier 11 is amplified and transmitted from the antenna 31 via the antenna switch 36. At this time, a part of the amplified high-frequency signal is input to the envelope detection circuit 13 via the loosely-coupled circuit 12 and the first switch 32, and is subjected to envelope detection. Circuit 14
Then, the amplification factor of the high frequency amplifier 11 is changed according to the comparison result with the fixed voltage which is the reference level.

At the time of reception, the antenna switch 3
6, the first switch 32 and the second switch 33 are shown in FIG.
Is switched to the connection state opposite to the state shown in FIG. That is, the antenna switch 36 connects the antenna 31 and the loosely coupled circuit 35, the first switch 32 connects the loosely coupled circuit of the envelope detection circuits 13 and 35, and the second switch 33 also performs level comparison. The circuit 14 and the bias switching circuit 34 are connected.

First, a received signal input from the antenna 31 passes through the loose coupling circuit 35 and the first switch 32,
The signal is input to the envelope detection circuit 13, subjected to envelope detection, and sent to the level comparison circuit 14. The level comparison circuit 14 calculates the difference between the level of the received signal and the fixed voltage, and sends the difference signal to the subsequent bias switching circuit 34.

As described above, the bias switching circuit 34
When the difference between the received signal level and the reference voltage is large, the gate voltage of the high-frequency amplifier 21 is reduced to reduce the amplification factor. Therefore, when a large signal is input to the antenna 31, the high-frequency amplifier 21 Is sent to the subsequent mixing circuit 22 without amplifying it so much.

[0024]

As described above, according to the present invention, it is possible to prevent a signal having a high level from being sent to the mixing circuit, and to use an element having low linear performance as the mixing circuit, thereby improving the economic efficiency. it can. Further, since the configuration for realizing the above effects can be used with the envelope detection circuit and the level comparison circuit which are conventionally provided, the configuration is more economical and more compact than those newly provided. Can be something.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a transceiver system of the present invention.

FIG. 2 is a circuit diagram around a bias switching circuit.

FIG. 3 is a circuit diagram of a conventional transceiver system.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 transmitter 11 high-frequency amplifier 12 loosely-coupled circuit 13 envelope detection circuit 14 level comparison circuit 20 receiver 21 high-frequency amplifier 22 mixing circuit 31 antenna 32 first switch 33 second switch 34 bias switching circuit 35 loosely-coupled circuit 36 antenna switch

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04B ^7/ 24-7/26 102 H04Q 7/00-7/38 H04B 1/04 H04B 1/38-1 / 58

Claims (1)

(57) [Claims] 1. A transmitter and a receiver are selectively connected to an antenna via an antenna switch. In the transmitter , a phase-modulated high-frequency output is detected by an envelope detection circuit, and then a level comparison is performed. compared with a reference level in the circuit, and configured to control the transmission output level in comparison of that, the receiver is amplifying the received signal from the antenna
Transceiver system equipped with a high-frequency amplifier
Te, the input side of the envelope detection circuit, the antenna switch, when said transmitter and said antenna is connected, enter the high-frequency output signal of the transmitter to the envelope detection circuit, and the antenna when it said the receiver is connected, before
Serial first switch is provided to receive signals from the antenna switch to enter the envelope detection circuit, while the output side of the level comparison circuit, by the first switch, the high-frequency output signal of the transmitter when There being input to the envelope detection circuit, switched to control the transmission output level by the output of said level comparator circuit, wherein the received signal by the first switch is input to the envelope detection circuit It is time, transceiver system, wherein the second switch switches to control the amplification factor of the high frequency amplifier at the receiver side by the output of said level comparator circuit is provided.